An important requirement for such resistors and resistive films is that a low temperature coefficient of resistance (TCR) be provided. This requirement becomes increasingly difficult to achieve in practice as the sheet resistivity increases. A further requirement for use in integrated circuits (IC) is compatibility with standard semiconductor process technology. The present invention achieves high resistance films of controllable resistivity (10 Mohm/cm.sup.2 to 10.sup.6 Mohm/cm.sup.2 ) with a low temperature coefficient of resistance. Such films are compatible with IC technology.
In the prior art, semi-insulating films have been prepared with high sheet resistance, but also having a high temperature coefficient of resistance. Typically, such devices have a high negative TCR of -70,000 parts per million. The preparation of high resistivity films may be by a low pressure chemical vapor deposition technique wherein a mixture of silane (SiH.sub.4) and nitrous oxide (N.sub.2 O) is allowed to react in a heated and partially evacuated chamber to deposit a thin film of material over the surface of a substrate. Typical deposition conditions are: temperature 650.degree. C., pressure 0.5 Torr, and SiH.sub.4 /N.sub.2 O ratio 4:1. Such a film is subsequently annealed at about 900.degree. C. This film consists of small silicon crystallites embedded in a silicon dioxide matrix, and will be referred to as the semi-insulating film.